Directions

Cut off roots and trim dark green tops from leeks; cut each leek lengthwise in half, then crosswise into 3/4-inch slices. Rinse leeks in large bowl of cold water, swishing to remove sand; transfer to colander to drain, leaving sand in bottom of bowl.

Place potatoes, celery root, and squash in 4 1/2- to 6-quart slow cooker. Stir in broth, thyme, salt, pepper, leek mixture, and 1 cup water. Cover slow cooker with lid and cook on low setting as manufacturer directs, 7 to 8 hours or until all vegetables are very tender.

With slotted spoon, transfer about 2 cups cooked vegetables to small bowl. With potato masher, pastry blender, or fork, coarsely mash vegetables. Stir mashed vegetables back into slow cooker, then stir in half-and-half; heat through on high setting, if necessary.